While 1,2,3,4-tetrahydroquinoline and benzyl alcohol are fine high-temperature (>400 degrees C) thermal stabilizers that efficiently inhibit the thermal degradation of dodecane, jet fuels, and similar hydrocarbon mixtures, kinetic studies reveal that the rate of dodecane degradation in the mixtures is a very strong function of temperature above 400 degrees C. In fact, we conclude that it will be extremely difficult to adequately stabilize hydrocarbon fuels using hydrogen donors at temperature much above 500 degrees C.